Who makes the best homemade baked goods! LOL....just kidding.
Seriously, perhaps split the group up into buddy teams and the teams have to work together to support each other, help each other eat healthy, exercise with each other, give each other moral pep-talks each day on the phone, etc. The team, as a whole, who loses the most weight at the end of the time period (say 8 weeks?) wins an exercise club membership or a spa treatment or something. Of course, weighing in and measuring should be done weekly to be sure they are losing weight in a healthy manner. And they can share their "buddy" stories with the other buddy teams so everyone learns from each other.
at 7:47 AM on Jan. 3, 2009